Overlooking the bay are the ruins of a mediaeval castle, which was restored in the sixteenth century. Vasco da Gama (1468-1524) is said to have been born here, being the son of the governor general of Sines. One of the castle towers houses a small museum collection dedicated to this famous navigator.

Sines also has a very interesting Archaeological Museum, which contains all the archaeological remains found in the region that testify to its occupation in more remote times.